PECULIARITIES OF STRUCTURAL AND ELECTROKINETIC PROPERTIES OF HfNi1-xCuxSn SOLID SOLUTION

A. Horyn, L. Romaka, Yu Stadnyk, V. Romaka, V. Pashkevych, M. Rokomanyuk


DOI: http://dx.doi.org/10.30970/vch.6401.128

Abstract


The effect of doping of half-Heusler phase HfNiSn (MgAgAs structure type) by Cu atoms on the structural, electrokinetic, and energetic characteristics of the semiconductive solid solution HfNi1‑xCuxSn was studied in the ranges: T = 80–400 K, x = 0–0.07. The samples of the HfNi1-xCuxSn solid solution were synthesized in an electric arc furnace. Homogenizing annealing was carried out at 1073 K for 720 hours. Powder diffraction data were obtained on a powder diffractometer STOE STADI-P (Cu Kα1-radiation). Structural characteristics are calculated using WinCSD program package.The temperature and concentration dependences of electrical resistivity ρ and thermopower coefficient α (relative to copper) were measured in the temperature range Т=80–400 K. X-ray phase and structural analyses revealed the absence of traces of foreign phases on the diffraction patterns of the HfNi1-xCuxSn samples except for the main phase, which is indexed in the structure type MgAgAs. The study of the semiconductive solid solution HfNi1-xCuxSn established an increase of the unit cell parameter a(x) at concentrations x=0–0.07, caused by the substitution of Cu atoms in the 4c position of Ni atoms and the generation of structural defects of a donor nature. The fact that at a concentration x>0.07 the values of the unit cell parameter a(x) decrease may indicate the solubility limit of Cu atoms. Changes in the crystal structure of HfNi1-xCuxSn are accompanied by changes in the electronic structure and the appearance of an additional donor band ɛD2 in the band gap.

The presence of high- and low-temperature activation on the ln(ρ(1/T,х)) dependencies of HfNi1‑xCuxSn indicates the location of the Fermi level εF in the band gap εg, near the conduction band εС, and electrons are the main current carriers. It was shown that the studied HfNi1-xCuxSn solid solution is a promising thermoelectric material.

 

Keywords: electrical conductivity, thermopower coefficient, Fermi level, structural defect.

 


References


Romaka V. V., Romaka L. P., Krayovskyy V. Ya., Stadnyk Yu. V. Stannides of rare earth and transition metals // Lviv Polytech. Univ. 2015. 221 p. [in Ukrainian].

Romaka V. V., Rogl P., Romaka L. et al. Peculiarities of structural disorder in Zr- and Hf-containing Heusler and half-Heusler stannides. Intermetallics. 2013. Vol. 35. P. 45–52. DOI: https://doi.org/10.1016/j.intermet.2012.11.022

Akselrud L., Grin Yu. WinCSD: software package for crystallographic calculations (Version 4) // J. Appl. Cryst. 2014. Vol. 47. P. 803–805.
DOI: https://doi.org/10.1107/S1600576714001058

Shklovskii B. I., Efros A. L. Electronic Properties of Doped Semiconductors // Springer-Verlag. Berlin; Heidelberg, 1984. 324 р. DOI: 10.1007/978-3-662-02403-4

Mott N. F., Davis E. A. Electronic Processes іn Non-crystalline Materials // Clarendon Press. Oxford, 1979.

Stadnyk Yu., Romaka L., Romaka V. V., Krajovskii V., Horyn А. Investigation of electrokinetic, magnetic and energy state characteristics of TiNi1-xCuxSn semiconductive solid solution // Visnyk Lviv Univ. Ser. Chem. 2018. Vol. 59(1). P. 123–130. DOI: https://doi.org/10.30970/vch.5901.123

Romaka V. V., Stadnyk Yu., Romaka L., Korzh R., Krajovskii V. Investigation of HfNiSn1-xSbxsemiconductive solid solution. 1. Crystal and electronic structures // Visnyk Lviv Univ. Ser. Chem. 2014. Vol. 55. P. 142-148.


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